Compound boost.

[EAGLE5]

To clarify, a trolling is about minimum effort for maximum trollage. This is more car masturbation in public. A bit of autoeroticism if you will.

[ajc209]

I like how the thread started, but then descended into chaos with talk of mid mounting engines and the like.

[Jaden]

The mid engine is a separate project altogether. I plan on getting a flooded out twin and doing that later. The compound boost will be front engine and potentially rear transaxle down the line with a torque tube.

This is not automasturbation. I am in the middle of a divorce so some things are on hold, but I am actively working on these projects.

My current project I'm not talking about (because I'm planning on putting on a little contest here about it) other than to say it is staying a stock block, but I am currently rebuilding a block for this and taking the measurements and what not for fabbing up some of the stuff.

As far as using the G96 transaxle... You use it the same way mid engine cars have used the G50, in fact many of the G96's have the same bolt pattern as the G50's and can use the same adapter plates.

Yes, using it will require some major fabbing. In particular, cutting the suspension frame and reinforcing it around the transaxle.

Since the hood will be retrofitted to be the new trunk and I'll be building a roll cage in the rear for supporting the engine and stiffening everything, that shouldn't be an issue.

For the mid engine conversion, the car will look completely different and I was looking at using the G96 precisely because of the closeness of the axles to the bell housing since space behind the front seats is limited.

reinforcing of the suspension frame will also be done via a transaxle crossmember that will bolt onto it underneath the transaxle as a trans mount.

Now we're derailing this thread too.

As to the dude who commented that I am confused as to where the flow comes from... Sorry I'm not..Please point out how ANYTHING I've said is wrong.

The FI system that takes air from ambient is the ONLY one that is responsible for air flow PERIOD!!!!

You could have three turbos or other FI systems in a row making 150PSI of boost, but you will only get the airflow that the first one that pulls from ambient has at the boost level it's running itself.

This is REALLY common in the diesel community.

Basically, compound boost works by taking ambient air and boosting it so that follow on systems have a denser starting charge that the follow on systems then compress.

It's a slight misnomer to say that the secondary's flow doesn't matter. It does but the primary HAS to be able to flow the amount of air you need at the boost level it will be running.

It becomes complex determining how much flow the secondary needs, but it's no where near what the primary needs to flow.

We can get into that if you guys would like to.

Jaden

p.s. as far as the auto tranny in the twins handling the power, I am not talking out of my ass here. It isn't me saying it at all. When I was looking into getting beefed up internals for the auto trans, the only company that was doing it had stopped doing and had put out that with a trans cooler, the twins' auto is capable of handling 650hp, don't know how accurate that is since trans capabilities aren't measured in hp but instead torque, but that's why I have an extra trans, and if I have to upgrade to a V160 or t56 with adapters down the road, so be it. Or if I can pull off the porsche transaxle with a torque tube, then I will for better weight distribution.

[Dipstik-sportech]

Compound boost with two types of forced induction that have the same boost characteristics hmmmmm. Can't say it will work the way you hope it will. The reason people use roots style blowers with big turbos is to get rid of lag. A centrifugal supercharger works much like a turbo in that it makes little to no boost at low rpm then ramps up as rims increase.

[Mr.ac]

I don't know about all that work to a mid engine car from a front engine car.
I would put all that money and effort into a Factoty 5 GTM. In the end you'll have a Frankenstein 86 or a nice GTM thats better in every way.
But that's just me.

Or just make your own frame and drop a 86 shell. Much easier that way.

[johl]

I sincerely hope you prove me wrong but from my 15+ years of being involved in the car scene I have noticed there are 2 types of people.

The first make threads on how they are going to put 'X' engine in their car or re-invent the wheel and then proceed to do nothing.

The second type of person says nothing and produces a complete car with 'X' engine already in it and running.

[enjetek]

excellent


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[FRS Justin]

Originally Posted by Dipstik-sportech

Compound boost with two types of forced induction that have the same boost characteristics hmmmmm. Can't say it will work the way you hope it will. The reason people use roots style blowers with big turbos is to get rid of lag. A centrifugal supercharger works much like a turbo in that it makes little to no boost at low rpm then ramps up as rims increase.

[ame="https://www.youtube.com/watch?v=JQXTPcMbAqc"]Twin charged gt86. Fully custom built by me. - YouTube[/ame]


[ame="https://www.youtube.com/watch?v=_vXrzFYHj0o"]WTF-86 Twincharged FA20, engine run-in on dyno - YouTube[/ame]


Those crafty Aussies did it 3 years ago.....

[Stimmed]

Both of those cars never saw the street though. The first vid was of Jet86 I think and that made lots of claims to never prove any of his power claims and it was never actually seen. WTF86 made that power on the dyno but had issues so went right back to a big single and now moving onto an r35 engine to truely make it insane.

[Jaden]

Originally Posted by Dipstik-sportech

Compound boost with two types of forced induction that have the same boost characteristics hmmmmm. Can't say it will work the way you hope it will. The reason people use roots style blowers with big turbos is to get rid of lag. A centrifugal supercharger works much like a turbo in that it makes little to no boost at low rpm then ramps up as rims increase.

Ummm yeah, two types of forced induction that are the same is the most common compound boost setup... Take a look here...https://www.dieselpowersource.com/ and here... http://cppdiesel.com/compound-turbo-kits-parts/ At that last one there's even a triple turbo setup.

Diesels can get away with that because they work off of compression so no danger of detonation. Like I stated, it's a slightly different principle but the same rules apply.

As I pointed out in the other thread. Look at the compressor map of a medium-large S/C. I attached a map for a vortech SI trim. It provides 40+lbs minute at like 4 psi.

The problem with using a large S/C in a low displacement engine is that it can't take that much air, but that's the beauty of compound boost.

A small fast spooling turbo can increase the boost of all of that air really quickly and low in the rpm range so you get early torque cause instead of running 4 psi at 3000rpm, you're compounding it with the turbo and running 13 psi, so the engine at 13 psi can handle 40lbs/min.

Then as the s/c increases boost, your intake manifold reference goes up sooner and you can decrease the PR of your turbo so that total boost remains the same or let total boost increase as the s/c increases its boost with engine rpm increase. You get the benefits of a large displacement engine and a broad torque curve with a small displacement engine and the linear gains you would see from a PD S/C. The s/c then increases it's boost at higher rpms to run say a total of 9 psi which on the SI trim provides 70-80 lbs/minute.


It gives you more control over the torque curve because you have large air flow at ALL rpms.

Plus it's not as complex as a large turbo into small turbo compound boost setup because you only have to control the boost levels via one turbo since the s/c increases linearly.

Jaden

[Jaden]

Originally Posted by johl

I sincerely hope you prove me wrong but from my 15+ years of being involved in the car scene I have noticed there are 2 types of people.

The first make threads on how they are going to put 'X' engine in their car or re-invent the wheel and then proceed to do nothing.

The second type of person says nothing and produces a complete car with 'X' engine already in it and running.

Yeah, I have been working quietly on it. I was following the WTF-86 thread and when he gave up on it claiming he couldn't make the power he was wanting to with the setup I wanted to know why, because there's no reason that he shouldn't have been able to.

This all started when I pointed out the biggest mistake most people make when trying to compound boost. That's using too small of a turbo as the primary because they simply don't understand that a 1000hp capable turbo will NOT be able to provide 1000hp in a compound setup because it has to provide that airflow lower in it's PR range in a compound boost setup.

That's why people always say a turbo will provide more power by itself. Well, the reality is that in a low displacement engine, having more top end power doesn't really help all that much. It becomes a dyno queen.

You need a broad torque curve to really use the power. That's why I linked to a DSM that was only making 600hp in a compound turbo setup but running 8's!!!!! and it was NOT AWD, it was converted to RWD.

That's why I created this thread and even discussed what I'm working on at all.

I don't want people to get the wrong idea from people who have done it the wrong way. You HAVE to have a primary FI system that provides the total airflow you need at the boost level it will be running BY ITSELF because as soon as you compound the boost it becomes a closed system and you can't get any additional airflow.

The mid engine thing is just another idea I've been tossing around, and have done preliminary measurements and design of fabrication necessary for... Let's not let that distract us from the point of the thread.

This thread is to discuss the potential of, the pitfalls associated with and the benefits of compound boost.

I won't be able to do any testing of this idea until I finish building up the motor which won't happen until after my divorce is final.

I am still working on the other project for now still and will hopefully have some major progress in the next couple of months.

I can't provide the progress pics I have on it yet because of the contest I plan on having here when it's done.

Jaden

p.s. This can get a bit confusing when looking at diesels because they are trying to go beyond the limits of a single turbo's PR. That's why I said it's a slightly different concept but the same rules apply.

In a diesel compound turbo setup because you're running higher total boost levels, you can get a primary turbo that has a 1200hp limit if you want the airflow to make 1200hp. This is because you can run 40psi of boost in the primary and 25 in the secondary to make a total boost of ~151psi or 15 psi in the secondary for a total boost of ~109psi but either way there you can go by the upper limit of the capability of the primary and don't have to worry about the airflow at the pr you are running as much.

You run 151 psi in a gas car and it's going boom. so you're dealing with lower PRs which means you have to be aware of the air flow at the pr you'll be running for that primary.

If you want to run 70-80 lbs a minute and 750hp with a total boost of 45 psi, you need a turbo or s/c that has a 70-80lb/min airflow at a pr of 2.0 or less if you want to get any benefit out of it. If wtf-86 was running a GTX3076R like the other guy was running it only puts out 45-50lbs/min at 2.0 PR. so you aren't going to get more than 500 hp at 45 psi if you're secondary runs at 10psi which in his case with the pos disp. s/c, was likely the case.

With a bigger turbo, say a t88 which pushes out 80lbs/min at a pr of 2.0 you'll no longer have the bottle neck at the primary turbo and at 45 psi you'll be able to make 800hp if the car can breathe that much air at 45 psi.

[EAGLE5]

I've seen people follow through on big projects. One guy supercharged his 550i and converted it to manual. It was a weird project, but it sounded better than any car ever. He also started by posting photos. If you're posting in the idea stage, it'll go nowhere.

[FRS Justin]

What about this one


[ame="https://www.youtube.com/watch?v=3Af9zKvWEVA"]Toyota 86 supercharged and turbocharged update, 86 Project with ROH DYNO FLEX FUEL RESULTS - YouTube[/ame]


[ame="https://www.youtube.com/watch?v=yd3pq_KDVDg"]Toyota GT86 Supercharged & Turbocharged | 86 Project | Drive.com.au - YouTube[/ame]

[CSG Mike]

There's some monkey math going on here...